Mobile wireless communications device with reduced microphone noise from radio frequency communications circuitry

ABSTRACT

A mobile wireless communications device includes a housing and circuit board in the housing and having radio frequency (RF) circuitry and a power amplifier and microphone mounted thereon. An antenna is carried within the housing and operative with the RF circuitry. An RF shield surrounds and isolates the microphone from the RF circuitry, power amplifier and antenna and shields the microphone from radiated energy generated from the RF circuitry, antenna or power amplifier.

RELATED APPLICATION

This application is based upon prior filed copending provisionalapplication Ser. No. 60/605,751 filed Aug. 31, 2004.

FIELD OF THE INVENTION

The present invention relates to the field of communications devices,and more particularly, to mobile wireless communications devices andrelated methods.

BACKGROUND OF THE INVENTION

Cellular communication systems continue to grow in popularity and havebecome an integral part of both personal and business communications.Cellular telephones allow users to place and receive phone calls mostanywhere they travel. Moreover, as cellular telephone technology isincreased, so too has the functionality of cellular devices. Forexample, many cellular devices now incorporate Personal DigitalAssistant (PDA) features such as calendars, address books, task lists,calculators, memo and writing programs, etc. These multi-functiondevices usually allow users to wirelessly send and receive electronicmail (email) messages and access the internet via a cellular networkand/or a wireless local area network (WLAN), for example.

As the functionality of cellular communications devices continues toincrease, so too does demand for smaller devices that are easier andmore convenient for users to carry. As any circuit boards and electroniccomponents thereon are reduced in size and placed closer together,including antenna and microphone components, various electroniccomponents can pick up conductive energy and create interference withinthe system. For example, an internal surface mounted microphone couldpick up conducted energy directly from a power amplifier or from theradiated energy emitted by an antenna. This unwanted reception ofconducted/near field radiated energy from power amplifiers and antennaeis particularly problematic in a packet burst transmission as part of aGlobal System for Mobile communications (GSM) system, including the 450MHz, 900 MHz, 1800 MHz and 1900 MHz frequency bands.

Other interfering signals can be generated when the liquid crystaldisplay (LCD) in some mobile wireless communications devices radiatesradio frequency (RF) interfering energy and degrades receiversensitivity. This is problematic where the interfering energy isgenerated by the microprocessor or central processing unit (CPU) of awireless mobile communications device and fed into the LCD lines, alongwith interfering energy generated by the LCD itself. Other problemsoccur when the conducted and radiated interfering radio frequency (RF)energy is coupled to the mobile wireless communications device causingaudio break through tests to fail for both the uplink and downlink. Eventhe keyboard circuits can create unwanted interference problems. Forexample, the radio frequency receiver sensitivity is often degraded bythe electromagnetic interference (EMF) of digital harmonics from themicroprocessor or CPU via the keyboard because of the resulting loopformed by any keyboard circuits. In some instances, strong RF energy,for example, the transmitted power from the radio via the antennainterferes with or couples to the microprocessor or CPU input/output(I/O) lines of a mobile wireless communications device through thekeyboard Key-In and Key-Out lines and causes a reset of themicroprocessor or CPU.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide isolationof a microphone used in a mobile wireless communications device fromradiated interfering energy, for example, such as generated from RFcircuitry, an antenna or power amplifier contained with thecommunications device.

A mobile wireless communications device, in accordance with the presentinvention, can be formed as a handheld transceiver, WLAN device orsimilar communications device. It includes a housing and a circuit boardcarried by the housing. Radio frequency (RF) circuitry and a poweramplifier are carried by the circuit board. A microphone is mounted onthe circuit board and operatively connected to the RF circuitry. Anantenna is carried within the housing and operative with the RFcircuitry. In accordance with one aspect of the present invention, an RFshield surrounds and isolates the microphone from the RF circuitry,power amplifier and antenna and shields the microphone from radiatedenergy generated from the RF circuitry, antenna or power amplifier. TheRF shield also changes the RF current distribution around themicrophone. The RF shield can be formed as a metallic housing secured tothe circuit board and surrounding the microphone. The RF circuitry couldinclude a transceiver chip set and be operative for generating GlobalSystems for Mobile (GSM) communication packet bursts.

In another aspect of the invention, a first isolation compartmentincludes RF circuitry, for example, a transceiver chip set, and a secondisolation compartment includes the power amplifier. The microphone andRF shield surrounding the microphone is positioned adjacent theseisolation compartments. The microphone in one example is preferablyformed as a surface mounted microphone. A cover can extend over thehousing at the microphone and an acoustical tube can extend from thecover through the RF shield to the microphone. This RF shield can have asound opening engaged by the acoustical tube, which is about 2.0 mm orless and configured for obtaining a desired frequency response. In yetanother aspect of the invention, an isolation ring can surround theacoustical tube between the cover and RF shield to provide RF andacoustical sealing. A method aspect of the invention is also set forth.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the detailed description of the invention whichfollows, when considered in light of the accompanying drawings in which:

FIG. 1 is a schematic block diagram of an example of a mobile wirelesscommunications device configured as a handheld device that can be usedwith the present invention and illustrating basic internal componentsthereof.

FIG. 2 is a front elevation view of the mobile wireless communicationsdevice of FIG. 1.

FIG. 3 is a schematic block diagram showing basic functional circuitcomponents that can be used in the mobile wireless communications deviceof FIGS. 1-2.

FIG. 4 is front elevational view of the mobile wireless communicationsdevice in accordance with one embodiment of the present invention havingthe front cover removed to illustrate an example of RF circuitry, poweramplifier, surface mounted microphone and noise isolation componentsassociated thereof.

FIG. 5 is an enlarged fragmentary sectional view of greater details ofthe microphone and associated noise isolation components of FIG. 4.

FIG. 6 is a schematic circuit diagram of an LCD display connector andassociated filter components that can be used with the mobile wirelesscommunications device of FIGS. 1-3 in accordance with one embodiment ofthe present invention.

FIG. 7 is a schematic circuit diagram of a LCD display connector andassociated filter components that can be used with a mobile wirelesslocal area network (WLAN) communications device in accordance withanother embodiment of the present invention.

FIG. 8A is a schematic circuit diagram of a first embodiment of an audiocircuit as part of an RF circuit having audio filtering components thatcan be used with the mobile wireless communications device of FIGS. 1-3.

FIG. 8B is a schematic circuit diagram of a second embodiment of anaudio circuit as part of an RF circuit having audio filtering componentsthat can be used with the mobile wireless communications device of FIGS.1-3.

FIG. 9 is a schematic circuit diagram of another embodiment of an audiocircuit as part of an RF circuit similar to FIGS. 8A and 8B, but havinga different circuit footprint and different positioning of audiofiltering components.

FIG. 10A is an example of a keyboard connector that can be used in themobile wireless communications device shown in FIGS. 1-3, and adapted tohave electromagnetic interference (EMI) filtering components connectedthereto.

FIG. 10B is a schematic circuit diagram of one example of EMI filteringcomponents that can be connected to the keyboard connector shown in FIG.10A and operative for filtering when communications signals arereceived.

FIG. 11A is a schematic circuit diagram of an example of a key arraythat can be used in a mobile wireless local area network (WLAN)communications device and adapted to have EMI filtering componentsconnected thereto.

FIG. 11B is a schematic circuit diagram of an EMI filtering componentsthat can be connected to the key array shown in FIG. 11A for filteringwhen signals are received.

FIG. 12 is a schematic circuit diagram showing a key array and EMIfiltering components connected between the key array and keypadconnector, all connected on a keyboard, and adapted for use in themobile wireless communications device shown in FIGS. 1-3 and operativefor filtering when signals are transmitted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout, and prime notation is used toindicate similar elements in alternative embodiments.

The interference problems created when an internal microphone, forexample, a surface-mounted technology (SMT) microphone “picks-up” orreceives conducted energy directly from a power amplifier and/or from anantenna during a GSM transmitter packet burst are overcome with thepresent invention. The use of an appropriate RF shielding and filters inone non-limiting example reduces the audible buzz in an audio circuit,for example, as used in the mobile wireless communications device ofFIGS. 1-3. In one non-limiting example, a separately isolated radiofrequency (RF) shield covers the internal microphone and its associatedcircuitry to prevent conducted and near field radiated energy emitted bya power amplifier from interfering with the microphone operation. The RFshield also provides adequate isolation from the radiated energy emittedby the antenna during a GSM packet burst. This RF shield is operative inconjunction with an acoustic seal to ensure a good acoustic frequencyresponse.

The different non-limiting embodiments and examples of the presentinvention described throughout the following description offers severaladvantages over prior art mobile wireless communications devices,systems and associated methods. By adding electromagnetic interference(EMI) filters to liquid crystal display (LCD) connection lines, thecentral processing unit (CPU) or microprocessor noise is prevented fromreaching the LCD. As a result, the prior art problems associated with anLCD radiating radio frequency (RF) interfering energy and causingdegradation of receiver sensitivity, or the microprocessor or CPUgenerating any interfering energy, is overcome. These prior artdisadvantages have been overcome in one particular embodiment of theinvention by adding filter components to the LCD circuitry andeliminating any noise before it can be radiated by the LCD and interferewith a received signal.

The prior art problems associated with the electromagnetic interference(EMI) in an audio break-through test for communications devices such asshown in FIGS. 1-3 is also overcome by reducing the conducted andradiated interfering RF energy that is coupled to the mobile wirelesscommunications device, which could create an audible noise and cause RFimmunity failure in both the uplink and downlink communications. An EMIfilter can be added to the microphone, a USB connector, speaker audiocircuits and headset connector at desired circuit points to eliminatethe conducted interfering RF energy from the coupling to the audiocircuits via a USB charging cable and the radiated, interfering RFenergy that is coupled to any audio circuits resulting from the pick-upon a headset cable or other similar connector.

The present invention also overcomes the prior art electromagneticinterference problems associated when the sensitivity of a radiofrequency receiver such as the type shown in FIGS. 1-3 is degraded byany electromagnetic interference, for example, digital harmonics fromthe microprocessor or CPU via the keypad (keyboard). It is known thatthe sensitivity of the RF receiver is significantly degraded by thedigital noise generated from the microprocessor or other CPU through theKey_In/Key_Out lines and into the keyboard traces and picked-up by theantenna. By adding within the keyboard traces and Key_In/Key_Out lines,EMI filter circuit, for example, filter array such as formed from seriesresistors or inductors, shunt capacitors, series EMI ferrite beads or acombination of resistor, inductor and capacitor, and ferrite beads, thereceiver sensitivity is improved.

The present invention also overcomes the prior disadvantages when strongRF energy, for example, the transmitted power from a mobile wirelesscommunications device such as shown in FIGS. 1-3 and its antennainterferes with or couples to the microprocessor or other CPUinput/output lines through the keyboard Key_In and Key_Out lines andcauses the microprocessor or CPU to reset. In accordance with onenon-limiting embodiment, series elements such as resistors can beapplied to the keyboard Key_In and Key_Out lines to dampen the RF energypicked up by these lines from either the generated internal energy orexternal interfering signals. Specific resistor values are selected toeliminate the RF energy, but also ensure normal CPU/keyboard operation.Other elements can be used, for example, series inductors, inductor andcapacitor, or ferrite beads.

A brief description will now proceed relative to FIGS. 1-3, whichdisclose an example of a mobile wireless communications device, forexample, a handheld portable cellular radio, which can incorporate thenon-limiting examples of the various circuits of the present invention.FIGS. 1-3 are representative non-limiting examples of the many differenttypes of functional circuit components and their interconnection, andoperative for use with the present invention.

Referring initially to FIGS. 1 and 2, an example of a mobile wirelesscommunications device 20, such as a handheld portable cellular radio,which can be used with the present invention is first described. Thisdevice 20 illustratively includes a housing 21 having an upper portion46 and a lower portion 47, and a dielectric substrate (i.e., circuitboard) 67, such as a conventional printed circuit board (PCB) substrate,for example, carried by the housing. A housing cover (not shown indetail) would typically cover the front portion of the housing. The termcircuit board 67 as used hereinafter can refer to any dielectricsubstrate, PCB, ceramic substrate or other circuit carrying structurefor carrying signal circuits and electronic components within the mobilewireless communications device 20. The illustrated housing 21 is astatic housing, for example, as opposed to a flip or sliding housingwhich are used in many cellular telephones. However, these and otherhousing configurations may also be used.

Circuitry 48 is carried by the circuit board 67, such as amicroprocessor, memory, one or more wireless transceivers (e.g.,cellular, WLAN, etc.), which includes RF circuitry, including audio andpower circuitry, including any keyboard circuitry. It should beunderstood that keyboard circuitry could be on a separate keyboard,etc., as will be appreciated by those skilled in the art. A battery (notshown) is also preferably carried by the housing 21 for supplying powerto the circuitry 48. The term RF circuitry could encompass theinteroperable RF transceiver circuitry, power circuitry and audiocircuitry.

Furthermore, an audio output transducer 49 (e.g., a speaker) is carriedby an upper portion 46 of the housing 21 and connected to the circuitry48. One or more user input interface devices, such as a keypad(keyboard) 23 (FIG. 2), is also preferably carried by the housing 21 andconnected to the circuitry 48. The term keypad as used herein alsorefers to the term keyboard, indicating the user input devices havinglettered and/or numbered keys commonly known and other embodiments,including multi-top or predictive entry modes. Other examples of userinput interface devices include a scroll wheel 37 and a back button 36.Of course, it will be appreciated that other user input interfacedevices (e.g., a stylus or touch screen interface) may be used in otherembodiments.

An antenna 45 is preferably positioned at the lower portion 47 in thehousing and can be formed as a pattern of conductive traces that make anantenna circuit, which physically forms the antenna. It is connected tothe circuitry 48 on the main circuit board 67. In one non-limitingexample, the antenna could be formed on an antenna circuit board sectionthat extends from the circuit board at the lower portion of the housing.By placing the antenna 45 adjacent the lower portion 47 of the housing21, the distance is advantageously increased between the antenna and theuser's head when the phone is in use to aid in complying with applicableSAR requirements. Also, a separate keyboard circuit board could be used.

More particularly, a user will typically hold the upper portion of thehousing 21 very close to his head so that the audio output transducer 49is directly next to his ear. Yet, the lower portion 47 of the housing 21where an audio input transducer (i.e., microphone) is located need notbe placed directly next to a user's mouth, and can be held away from theuser's mouth. That is, holding the audio input transducer close to theuser's mouth may not only be uncomfortable for the user, but it may alsodistort the user's voice in some circumstances. In addition, theplacement of the antenna 45 adjacent the lower portion 47 of the housing21 also advantageously spaces the antenna farther away from the user'sbrain.

Another important benefit of placing the antenna 45 adjacent the lowerportion 47 of the housing 21 is that this may allow for less impact onantenna performance due to blockage by a user's hand. That is, userstypically hold cellular phones toward the middle to upper portion of thephone housing, and are therefore more likely to put their hands oversuch an antenna than they are an antenna mounted adjacent the lowerportion 47 of the housing 21. Accordingly, more reliable performance maybe achieved from placing the antenna 45 adjacent the lower portion 47 ofthe housing 21.

Still another benefit of this configuration is that it provides moreroom for one or more auxiliary input/output (I/O) devices 50 to becarried at the upper portion 46 of the housing. Furthermore, byseparating the antenna 45 from the auxiliary I/O device(s) 50, this mayallow for reduced interference therebetween.

Some examples of auxiliary I/O devices 50 include a WLAN (e.g.,Bluetooth, IEEE 802.11) antenna for providing WLAN communicationcapabilities, and/or a satellite positioning system (e.g., GPS, Galileo,etc.) antenna for providing position location capabilities, as will beappreciated by those skilled in the art. Other examples of auxiliary I/Odevices 50 include a second audio output transducer (e.g., a speaker forspeaker phone operation), and a camera lens for providing digital cameracapabilities, an electrical device connector (e.g., USB, headphone,secure digital (SD) or memory card, etc.).

It should be noted that the term “input/output” as used herein for theauxiliary I/O device(s) 50 means that such devices may have input and/oroutput capabilities, and they need not provide both in all embodiments.That is, devices such as camera lenses may only receive an opticalinput, for example, while a headphone jack may only provide an audiooutput.

The device 20 further illustratively includes a display 22, for example,a liquid crystal display (LCD) carried by the housing 21 and connectedto the circuitry 48. A back button 36 and scroll wheel 37 can also beconnected to the circuitry 48 for allowing a user to navigate menus,text, etc., as will be appreciated by those skilled in the art. Thescroll wheel 37 may also be referred to as a “thumb wheel” or a “trackwheel” in some instances. The keypad 23 illustratively includes aplurality of multi-symbol keys 24 each having indicia of a plurality ofrespective symbols thereon. The keypad 23 also illustratively includesan alternate function key 25, a next key 26, a space key 27, a shift key28, a return (or enter) key 29, and a backspace/delete key 30.

The next key 26 is also used to enter a “*” symbol upon first pressingor actuating the alternate function key 25. Similarly, the space key 27,shift key 28 and backspace key 30 are used to enter a “0” and “#”,respectively, upon first actuating the alternate function key 25. Thekeypad 23 further illustratively includes a send key 31, an end key 32,and a convenience (i.e., menu) key 39 for use in placing cellulartelephone calls, as will be appreciated by those skilled in the art.

Moreover, the symbols on each key 24 are arranged in top and bottomrows. The symbols in the bottom rows are entered when a user presses akey 24 without first pressing the alternate function key 25, while thetop row symbols are entered by first pressing the alternate functionkey. As seen in FIG. 2, the multi-symbol keys 24 are arranged in thefirst three rows on the keypad 23 below the send and end keys 31, 32.Furthermore, the letter symbols on each of the keys 24 are arranged todefine a QWERTY layout. That is, the letters on the keypad 23 arepresented in a three-row format, with the letters of each row being inthe same order and relative position as in a standard QWERTY keypad.

Each row of keys (including the fourth row of function keys 25-29) isarranged in five columns. The multi-symbol keys 24 in the second, third,and fourth columns of the first, second, and third rows have numericindicia thereon (i.e., 1 through 9) accessible by first actuating thealternate function key 25. Coupled with the next, space, and shift keys26, 27, 28, which respectively enter a “*”, “0”, and “#” upon firstactuating the alternate function key 25, as noted above, this set ofkeys defines a standard telephone keypad layout, as would be found on atraditional touch-tone telephone, as will be appreciated by thoseskilled in the art.

Accordingly, the mobile wireless communications device 20 as describedmay advantageously be used not only as a traditional cellular phone, butit may also be conveniently used for sending and/or receiving data overa cellular or other network, such as Internet and email data, forexample. Of course, other keypad configurations may also be used inother embodiments. Multi-tap or predictive entry modes may be used fortyping e-mails, etc. as will be appreciated by those skilled in the art.

The antenna 45 is preferably formed as a multi-frequency band antenna,which provides enhanced transmission and reception characteristics overmultiple operating frequencies. More particularly, the antenna 45 isdesigned to provide high gain, desired impedance matching, and meetapplicable SAR requirements over a relatively wide bandwidth andmultiple cellular frequency bands. By way of example, the antenna 45preferably operates over five bands, namely a 850 MHz Global System forMobile Communications (GSM) band, a 900 MHz GSM band, a DCS band, a PCSband, and a WCDMA band (i.e., up to about 2100 MHz), although it may beused for other bands/frequencies as well. To conserve space, the antenna45 may advantageously be implemented in three dimensions although it maybe implemented in two-dimensional or planar embodiments as well.

The mobile wireless communications device shown in FIGS. 1 and 2 canincorporate e-mail and messaging accounts and provide differentfunctions such as composing e-mail, PIN messages, and SMS messages. Thedevice can manage messages through an appropriate menu that can beretrieved by choosing a messages icon. An address book function couldadd contacts, allow management of an address book, set address bookoptions and manage SIM card phone books. A phone menu could allow forthe making and answering of phone calls using different phone features,managing phone call logs, setting phone options, and viewing phoneinformation. A browser application could permit the browsing of webpages, configuring a browser, adding bookmarks, and changing browseroptions. Other applications could include a task, memo pad, calculator,alarm and games, as well as handheld options with various references.

A calendar icon can be chosen for entering a calendar program that canbe used for establishing and managing events such as meetings orappointments. The calendar program could be any type of messaging orappointment/meeting program that allows an organizer to establish anevent, for example, an appointment or meeting.

A non-limiting example of various functional components that can be usedin the exemplary mobile wireless communications device 20 of FIGS. 1 and2 is further described in the example below with reference to FIG. 3.The device 20 illustratively includes a housing 120, a keypad 140 and anoutput device 160. The output device 160 shown is preferably a display,which is preferably a full graphic LCD. Other types of output devicesmay alternatively be used. A processing device 180 is contained withinthe housing 120 and is coupled between the keypad 140 and the display160. The processing device 180 controls the operation of the display160, as well as the overall operation of the mobile device 20, inresponse to actuation of keys on the keypad 140 by the user.

The housing 120 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 180, other parts of the mobiledevice 20 are shown schematically in FIG. 3. These include acommunications subsystem 101; a short-range communications subsystem102; the keypad 140 and the display 160, along with other input/outputdevices 106, 108, 110 and 112; as well as memory devices 116, 118 andvarious other device subsystems 121. The mobile device 20 is preferablya two-way RF communications device having voice and data communicationscapabilities. In addition, the mobile device 20 preferably has thecapability to communicate with other computer systems via the Internet.

Operating system software executed by the processing device 180 ispreferably stored in a persistent store, such as the flash memory 116,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the random access memory (RAM)118. Communications signals received by the mobile device may also bestored in the RAM 118.

The processing device 180, in addition to its operating systemfunctions, enables execution of software applications 130A-130N on thedevice 20. A predetermined set of applications that control basic deviceoperations, such as data and voice communications 130A and 130B, may beinstalled on the device 20 during manufacture. In addition, a personalinformation manager (PIM) application may be installed duringmanufacture. The PIM is preferably capable of organizing and managingdata items, such as e-mail, calendar events, voice mails, appointments,and task items. The PIM application is also preferably capable ofsending and receiving data items via a wireless network 141. Preferably,the PIM data items are seamlessly integrated, synchronized and updatedvia the wireless network 141 with the device user's corresponding dataitems stored or associated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 101, and possibly throughthe short-range communications subsystem. The communications subsystem101 includes a receiver 150, a transmitter 152, and one or more antennae154 and 156. In addition, the communications subsystem 101 also includesa processing module, such as a digital signal processor (DSP) 158, andlocal oscillators (LOs) 161. The specific design and implementation ofthe communications subsystem 101 is dependent upon the communicationsnetwork in which the mobile device 20 is intended to operate. Forexample, the mobile device 20 may include a communications subsystem 101designed to operate with the Mobitex™, Data TAC™ or General Packet RadioService (GPRS) mobile data communications networks, and also designed tooperate with any of a variety of voice communications networks, such asAMPS, TDMA, CDMA, PCS, GSM, etc. Other types of data and voice networks,both separate and integrated, may also be utilized with the mobiledevice 20.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore requires a subscriber identitymodule, commonly referred to as a SIM card, in order to operate on aGPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 20 may send and receive communicationssignals over the communication network 141. Signals received from thecommunications network 141 by the antenna 154 are routed to the receiver150, which provides for signal amplification, frequency down conversion,filtering, channel selection, etc., and may also provide analog todigital conversion. Analog-to-digital conversion of the received signalallows the DSP 158 to perform more complex communications functions,such as demodulation and decoding. In a similar manner, signals to betransmitted to the network 141 are processed (e.g., modulated andencoded) by the DSP 158 and are then provided to the transmitter 152 fordigital to analog conversion, frequency up conversion, filtering,amplification and transmission to the communication network 141 (ornetworks) via the antenna 156.

In addition to processing communications signals, the DSP 158 providesfor control of the receiver 150 and the transmitter 152. For example,gains applied to communications signals in the receiver 150 andtransmitter 152 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 158.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 101and is input to the processing device 180. The received signal is thenfurther processed by the processing device 180 for an output to thedisplay 160, or alternatively to some other auxiliary I/O device 106. Adevice user may also compose data items, such as e-mail messages, usingthe keypad 140 and/or some other auxiliary I/O device 106, such as atouchpad, a rocker switch, a thumb-wheel, or some other type of inputdevice. The composed data items may then be transmitted over thecommunications network 141 via the communications subsystem 101.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 110, and signals fortransmission are generated by a microphone 112. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 20. In addition, the display 160 mayalso be utilized in voice communications mode, for example to displaythe identity of a calling party, the duration of a voice call, or othervoice call related information.

Any short-range communications subsystem enables communication betweenthe mobile device 20 and other proximate systems or devices, which neednot necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, or a Bluetooth™ communications module toprovide for communication with similarly-enabled systems and devices.

In accordance with a non-limiting example of the present invention, FIG.4 shows an example of a circuit layout on part of the circuit board 67that can be included within the mobile wireless communications device 20of FIGS. 1-3, and showing a front cover removed from a housing toillustrate a surface mounted microphone 200 and its circuitry andassociated noise isolation components as will be explained in greaterdetail below. The circuit board 67 includes radio frequency (RF)circuitry, for example, cellular telephone communications circuitry,which is mounted in first and second isolation shields or “cans”210,212, as often called by those skilled in the art, forming acompartment on the circuit board, each which receive the RF circuitry.Each can 210,212 forms a radio frequency isolation compartment and mayinclude sides and a top. The first can 210 includes a transceiver chipset 220, for example, a transmitter chip, receiver chip, and localoscillator chip as non-limiting examples with those chips labeled A, Band C. Other illustrated components could include the various resistors,capacitors, amplifiers, regulators and other circuit components commonto those devices, but not explained in detail.

Located outside first and second isolation cans 210,212, but mounted onthe circuit board 67, is a liquid crystal display (LCD) connector 230and a keyboard connector 232, as well as associated circuit components234. These components 230, 232 and 234 can be configured in differentconfigurations besides the configuration illustrated in the non-limitingexample of FIG. 4. The compartment within the second isolation can 212includes a power amplifier 236 and switch diplexer 238. Other components240 are mounted within the compartment and form the resistors,capacitors, transistors, and inductors necessary to drive the audio andpower circuits for the microphone, power amplifier and other circuits.

To provide microphone isolation, a radio frequency isolation shield 250,formed in the illustrated non-limiting example as a third isolation“can” 250, is positioned at a corner of the second “can” 212, and formsanother isolation compartment at this corner. The shield is formed as aseparate metallic housing secured to the circuit board and surroundingthe microphone, effectively covering, i.e., shielding the entiremicrophone. Although a “can” configuration formed as a metallic housingwith top and sides and is used for the RF shield, other configurationscould be used. The compartment formed by the isolation shield 250receives a microphone 200 formed preferably as a surface mountedmicrophone integrated circuit chip 200 on the circuit board 67. Asillustrated in this non-limiting configuration, this places themicrophone chip adjacent to the bottom center of the device 20 where thesound hole is typically located in the cover of a cellular phone orsimilar mobile wireless communications device. The present inventionovercomes the drawback when the microphone 200 is in relatively closeproximity to the RF circuitry such that the microphone picks-up unwantednoise. This is particularly problematic when the RF circuitry istransmitting Global Systems for Mobile communications (GSM) transmissionpacket bursts, for example, but not limited to GSM. This type of noiseoften results in an audible buzz during operation. Furthermore, thenoise problem can be further compounded by increases in diameter of anysound hole in the housing cover, even small diameter holes. This problemworsens as the diameter of the acoustical tube that connects the soundhole to the microphone increases.

To reduce this noise resulting from the RF circuitry, the metallicshield or “can” forming an isolation shield includes a side and topmetal wall, i.e., forming a complete isolation shield surrounding, i.e.,covering the microphone 200 and its associated circuitry to provideisolation from the RF circuitry. This isolation shield provides thenecessary isolation from the RF amplifiers and from any energy radiatedfrom the antenna.

FIG. 5 shows an enlarged, fragmentary, sectional view of the microphone200 of FIG. 4 when the communications device 20 is assembled and ahousing cover, such as including keyboard plastics, is positioned overthe housing and circuit board. The microphone 200 has an associatedassembly that includes a rubber or other polymer acoustical tube 252that connects a sound hole 254 in the housing cover 256 forming part ofkeyboard plastics with the microphone 200, which extends through a hole258 in the top of the microphone isolation shield 250. It should beunderstood that other suitable materials could also be used for theacoustical tube 252. The housing cover 256 could be formed from plasticor similar material and have access holes (not shown) for correspondingkeys of a telephone keypad, or in the case of a cellular phone with apersonal digital assistant (PDA) or e-mail/Internet capabilities, analphanumeric keypad, as appreciated by those skilled in the art andshown in FIG. 2 as a non-limiting example.

The keyboard plastics, such as shown in FIG. 5, are preferably formed asa separate keyboard positioned over the circuit board 67. This separatekeyboard includes a keyboard, i.e., keypad connector, which engages thekeyboard connector 232. Mounted on the keyboard are a keypad arraycircuit, the keypad or keyboard connector that engages the keyboardconnector on the main circuit board 67, and Key_In and Key_Out linesthat connect the keypad connector and the keypad array. These linescould be formed as signal traces. Examples of these components on akeyboard are shown in FIG. 12. This keyboard could be part of thehousing cover 256 or separate from the housing cover. Thus, throughoutthis description, the term housing cover is broad enough to encompassthe keyboard as a separate plastic or similarly configured keyboard orother support that covers all or a portion of the circuit board 67 andcontains the keypad connector, Key_In/Key_Out lines and keypad arraycircuit, such as shown in FIG. 12, as a non-limiting example.

In addition, an isolation ring 260 is positioned between the microphoneisolation shield 250 and the housing cover 256. This ring 260 surroundsthe acoustical tube 252. When the communications device 20 is assembledand the front housing cover 256 is installed, the downward force on thering 260 causes it to contact both the microphone isolation shield 250and the housing cover 256 to provide RF and acoustic sealing, as will beappreciated by those skilled in the art. The ring 260 is preferablyformed from a metal material. The isolation shield 250 and itsassociated ring 260 could be configured and dimensioned to provide adesired acoustic frequency response, as will be appreciated by thoseskilled in the art.

Representative distances as non-limiting examples for the configurationshown in FIG. 5 are now set forth. It should be understood that thesenon-limiting examples of dimensions can vary depending on the design,configuration, and frequencies used.

The distance between the housing cover 256 and the top surface isolationof microphone isolation shield 250 could be about 0.1 mm, for example,as indicated by dimension “A” and the sound hole 254 in the housingcover 256 could be about 2.0 mm or less as represented by the dimension“B”. The acoustical tube 252 may have a diameter of about 5.0 mm asrepresented by the dimension “C” and the diameter of the isolation ring260 can be about 10.0 mm as represented by the dimension “D”, asnon-limiting examples. Additional filters, such as ferrite chokefilters, for example, can be used inside the microphone isolation shield250 to reduce conducted interference to a greater extent, as will beappreciated by those skilled in the art. Furthermore, the microphoneisolation shield 250 can be implemented with devices other than cellulartelephones. For example, a portable, wireless local area network (WLAN)communications device may transmit voice/sound data over a WLAN deviceand thus include a microphone positioned in a similar manner to thatdiscussed above. Similar noise reduction components could be used asnon-limiting examples.

It should be understood that the acoustic channel formed within theacoustic tube 252 allows the communications device 20 to pass a specificacoustical mark for certification and allows a certain frequencyresponse out of the cavity and its microphone isolation shield 250,i.e., for network certification.

As noted before, the LCD in certain examples of the communicationsdevice 20 can radiate RF interfering energy and degrade receiversensitivity. Interfering energy can also be generated by the CPU of thecommunications device 20. This energy can be fed into the LCD lines,along with interfering energy generated by the LCD. FIG. 6 is aschematic circuit diagram showing a portion of a LCD circuit 290 havingan LCD connector 300 and its filter components associated therewith thatcan be used with the mobile wireless communications device of FIGS. 1-3.FIG. 7 shows a LCD display circuit 350, LCD connector 400 and filtercomponents operative with a wireless local area network (WLAN)communications device using similar features explained with reference tothe mobile wireless communications device of FIGS. 1-3. The dashed lineportion shown in FIGS. 6 and 7 indicates the general layout of LCDcircuit components that could be included on a circuit board, includingassociated filter components and LCD connection lines.

The LCD 160, such as shown in FIG. 3, has a microprocessor (or CPU) 180connection to the display 160 via an LCD connector 300 such as shown inFIG. 6. This connection is sometimes problematic because the LCDgenerates relatively high quality visual outputs but also generatesradio frequency (RF) energy. When used in a mobile wirelesscommunications device 20 such as a mobile handheld cellular phone, a PDAor a wireless local area network (WLAN) device, for example, the RFenergy from the LCD can cause interference with the RF components of thedevice because they are typically in relatively close proximity to eachother. This is particularly true with devices that use internalantennas, for example antennas positioned within a housing on a printedcircuit board (PCB) or other similar antenna.

These microprocessors or CPUs generally operate at fairly high clockspeeds, for example, based upon a 30 MHz clock signal which could beincreased to three or four times that speed for internal use by themicroprocessor. Thus, the microprocessor 180 may introduce harmonicsinto the connection lines to the LCD, which may in turn create furtherRF interference, as will be appreciated by those skilled in the art.

As shown in FIG. 6, electromagnetic interference (EMI) filters 310 areadvantageously connected to the connection lines 312 extending betweenthe microprocessor 180 and the LCD connector 300 to reduce theinterference caused by harmonics from the microprocessor 180. The dashedline 314 in FIG. 6 indicates a functional area on the circuit board 67which would include the various components, including the LCD connector300 and the EMI filters 310 associated with the LCD connector 300.

By way of example, EMI filters can include respective bypass capacitors320 connected between the LCD connection lines 312 and ground 322 asillustrated. The capacitors 320 that are shown in FIG. 6 can have avalue of about 68 pF. In association with the capacitors 320 and the LCDconnection lines 312 are EMI filters connected to the LCD circuitry toreduce the RF energy before it can be radiated by the LCD and interferewith the RF components. For example, the EMI filters can be EMI filters324 such as KNA series EMI filters manufactured by AVX Corp. Examples ofsuch filters include those sold under the designation as KNA 32200 andsimilar, KNA 32XXX series filters that are illustrated in theembodiments shown in FIGS. 6 and 7. Of course, other suitable EMIfilters can also be used.

The LCD connector 300 typically includes a mounting plate-to-ground pin,and in the illustrated example, two such mounting plate-to-ground pinsare labeled MP1 and MP2. The filters 324 are typically LC filters thatgive an excellent frequency response with respect to any attenuatingnoise coming from the microprocessor 180 to the LCD 160. These filters324 are particularly adequate with respect to different frequency bands,e.g., the GSM 900 MHz and PCS 1900 MHz. These filters give about 30 to40 decibel (dB) attenuation on these bands. Each filter 324 can beformed as a filter array as illustrated, for example, as an array ofinductors 324 a as illustrated.

The described LCD circuit can also include an LBAT terminal 330 and VBATterminal 332, each having an appropriate filter 325 as illustrated inFIG. 6, using a pie configuration of capacitors 326 and inductors 328for filtering.

FIG. 7 shows a LCD display circuit 350 that could be used with a mobilewireless communications device 20 such as a WLAN device and having asomewhat different circuit footprint configuration as compared to thecircuit footprint configuration shown in FIG. 6. Similar functionalcomponents in this embodiment are given reference numerals starting inthe 400 series. This circuit 350 uses 12 pF capacitors 420 connected toground 422, the LCD connector 400, and into the LCD connection lines412, which in turn, connect into the filter 424, formed as a filterarray as illustrated and similar to that shown in FIG. 6. In thisparticular embodiment, however, ferrite beads 460 or similar inductorcomponents are connected between the LCD connection lines 412 and thefilter arrays 424, as illustrated. The circuit configuration in FIG. 7is somewhat different than the circuit illustrated in FIG. 6 because aWLAN communications device would work at about 2.4 GHz. The ferritebeads 460 in combination with the capacitors 420 and filter arrays 424are found to enhance performance. A voltage regulator circuit 470 can beoperatively connected to the filter array 424, lines 412 and capacitors420 as illustrated, and include appropriate ground, enable, Vin and Voutterminals.

The KNA series of filters 324, 424 are a distributed constant type LCfilter that prevents ringing caused by circuit impedance. These types offilters are suitable for digital circuits and visual line circuits. Theyhave an excellent noise attenuation over wide frequency ranges and is alow profile of about H=1.0 mm thickness that is suitable for smallelectronic devices. They can have a cutoff frequency at above 200 MHzand 100 milliamp rated current with 25 volts DC.

Referring once again to FIG. 3, the wireless mobile communicationsdevice 20 such as a handheld cellular communications device, includes amicroprocessor (or CPU) 180, microphone 112, speaker 110, and serialcommunications port 108, such as an RS-232 or universal serial bus (USB)port, for example. The microphone 112 and speaker 110 are used for audio(i.e., voice) input and output during cellular telephone calls, forexample, as will be appreciated by those skilled in the art. The devicecan also include auxiliary input/output (I/O) connectors 106, such as aheadset connector, for example.

The serial port 108 can be used by the microprocessor 180 to communicatewith a host computer, for example. In particular, in certainembodiments, the device 20 can provide personal digital assistant (PDA)features, as well as e-mail/Internet capabilities. In this case, anycalendar, contacts, e-mails and similar functions can be synchronizedbetween the device 20 and a host computer by the microprocessor 180, aswill be appreciated by those skilled in the art. Moreover, the serialport 108 can be used for charging a battery of the device 20, e.g., byconnecting the serial port to an AC/DC converter.

While the serial port 108 provides a relatively easy and convenient wayfor users to charge this device 20, a drawback of this approach is theinterference that can be introduced onto the serial bus from an AC powersource. Also, various audio components of the device 20 (e.g., themicrophone 112, the speaker 110, headset connector, etc.) can besusceptible to interference from external RF sources, such as AM/FM orshort wave radio and similar transmissions. This is particularly true inthe 80 MHz to the 2 GHz frequency range, for example.

The susceptibility of the communications device 20 to interference overa serial bus during charging and/or from RF transmissions interferingwith the audio components decreases the overall interference immunity ofthe device. Some regulating bodies are now requiring wirelesscommunications devices to comply not only with interference guidelines(i.e., to not cause excessive interference), but also have a certainlevel of immunity to interference from other RF sources. By way of anexample, RnTte immunity testing is now required for many RFcommunications devices in Europe. Unfortunately, the test can be subjectto interference.

FIGS. 8A and 8B show a basic audio circuit 500, including serial busconnections that can be used for mobile wireless communications device20 shown in FIGS. 1-3. This circuit 500 now has certain types of valuesof filters placed around the device to reduce immunity. Basic audiocomponents are shown in the dashed rectangular box and include twomicrophone audio switches 502, which include a headset detect circuit504 that is triggered when the headset jack has an external speakermicrophone connected thereto. It detects the microphone and switches thelines over. At the receiver speaker 506 are two speaker audio switches510, each with a detect circuit 512 that detects when the earphone isconnected and switches the line over, and inductor component 514operative with the receiver speaker 506 and the audio switches 510. Aphysical jack is indicated at 520 and receives a jack input and connectsto headset detect line and terminal 521, which also includes a seriallyconnected inductor 522. The described components are connected togetherand operative with the microprocessor and other components, for example,various inductors, diodes, capacitors, resistors, and associated circuitcomponents.

To increase the immunity (i.e., reduce the susceptibility) of the device20 to electromagnetic interference (EMI), a plurality of EMI filters areadded to the audio and/or serial bus circuit 500 of the communicationsdevice 20. As shown in FIGS. 8A and 8B, for example, choke filters(i.e., inductors) can include respective individual inductors for thispurpose. A choke filter 540 is operatively connected into connectionline 542 between the physical jack 520 and the microprocessor 180. Thisconnection line 542 includes a capacitor circuit 544. Another chokefilter 550 is operatively connected to the microphone audio switches502. Yet another choke filter 560 is operatively connected to thephysical jack 520 and the microprocessor 180 on a connection line 562.Although the inductor or choke filters as illustrated and positioned inthe respective selected circuit positions, it should be understood thatother filters can be used for the present invention.

The choke filter 540 also can interconnect to a resistor divider circuit541 that includes resistors 541 a, 541 b for changing the bias on thechoke filter 540 as shown in FIG. 8B. This particular circuit layoutusing the resistor divider 541 shown in FIG. 8B is more sensitive todifferential AC and DC lines. The resistor divider circuit 541 allows adifferent bias, canceling some noise.

Other basic components included in FIGS. 8A and 8B include the testpoints 570 near the receiver speaker. Some proposed components andcircuit designs were removed. For example, a resistor circuit indicatedby the dashed X at 572 near the physical jack 520 and a transistorcircuit indicated by the dashed X at 574 were initially included in acircuit design and operatively connected to the ground connection of thephysical jack and the microprocessor. These circuits 572, 574 wereremoved as indicated by the dashed-out box.

FIG. 9 is a schematic circuit diagram for an audio circuit 580 thatincludes serial bus connections and having another circuit footprint,such as for a mobile wireless communications device 20, and showingsimilar components in a different configuration. Any similar componentshave been given the same reference numeral. This circuit 580 alsoincludes an operational amplifier circuit 581 operatively connected tothe microprocessor 180 and operative as a filter or buffer. FIG. 9 alsoshows a microphone circuit 582, which would be operative with microphoneaudio switches 502, even though in this fragmentary schematic circuitdiagram it is shown separate. Choke filter 583 is operatively connectedto the microphone circuit 582. A choke filter 584 is operativelyconnected to the physical jack 520 and the operational amplifier circuit581. Another choke filter 585 is operatively connected to a microphoneaudio switch 502. Other circuit components can be connected asillustrated in this non-limiting example.

A previously designed inductor RL filter as indicated by the dashedlines and crossed out “X” at 590 was found not to be as operative as thechoke filters as described and removed from the circuit design. Thechoke filters are advantageous at the frequency band about 40 MHz, whichhas a strong impact on the immunity performance of the radio. Criticalspots are selectively chosen for these ESP filters designed in theseexamples of choke filters. A capacitor circuit 586 is connected betweenoperational amplifier 581 and input jack 520 for determining connection.A transistor circuit 586 a is included in this design and operativelyconnected between the operational amplifier circuit 581 and intoconnection lines for the filter 584 and input jack 520. The circuit 580includes other components that are connected as illustrated in thisnon-limiting example.

By way of example, the choke filters as described with reference toFIGS. 8A, 8B and 9 could be ferrite filters, for example, although othersuitable filter components and/or materials may also be used, as will beappreciated by those skilled in the art. In addition to positioning theEMI filters to reduce unwanted interference, other components connectedto the audio and/or serial bus circuitry can be scrutinized to determineif interference susceptibility effects.

The use of the added choke filters advantageously reduces conductedinterfering energy introduced to the audio components via a serial(i.e., USB) charging cable and other sources. This further reducesradiated interfering RF energy introduced to the audio components viathe microphone 112 (FIG. 3) or the microphone of a connected headset,for example.

As noted before, the keypad (keyboard) and its associated circuitryconnected to other components can create interference. This can beespecially true when the keypad (keyboard) is in close proximity. FIGS.10A and 10E show a respective keyboard connector 600 that can be used inthe mobile wireless communications device shown in FIGS. 1-3 and haveEMI filtering components connected thereto. This keyboard connector 600includes appropriate LED pins and lines that connect to serial elementsas filtering components 602 and Key-Out and Key-In lines as shown inFIG. 10B. In the illustrated embodiment, the keyboard connector 600 is afemale connector and receives a male plug extending from the separatekeypad connector positioned on a separate keyboard and connects thereto.

FIG. 10B is a schematic circuit diagram of an example of EMI filteringcomponents 602 that can be connected to the keyboard connector 600 shownin FIG. 10A and used in the mobile wireless communications device ofFIGS. 1-3 and operative for filtering when receiving signals.

FIG. 11A is a schematic circuit diagram of a key array circuit 650 for akeypad, which can be used in a mobile wireless communications device 20such as a local area network (WLAN) communications device. This keyarray circuit 650 could be on a separate keyboard. FIG. 11B is aschematic circuit diagram of an example of the filtering components 652that can be connected either to the Key_In or Key_Out lines and used ina mobile wireless local area network (WLAN) communications device andoperative when receiving signals. It should be understood that the keyarray circuit 650 includes various Key_In and Key_Out and other linesand terminals as illustrated.

It should be understood that the microprocessor (or CPU) 180 as shown inFIG. 3 has a keypad (keyboard) 140 coupled to the microprocessor, andthe cellular communication subsystem 101. The cellular communicationsubsystem 101 includes a cellular receiver 150 and cellular transmitter152, and their respective associated antennas 154 and 156. Of course, itshould be noted that a single antenna can be used in certainembodiments.

The keypad 140 may be a numeric keypad for use in placing cellulartelephone calls, as will be appreciated by those skilled in the art.Moreover, in certain embodiments in which the device 20 advantageouslyprovides personal digital assistant (PDA) and/or email/Internetfunctionality, the keypad 140 may include alphanumeric keys and otherfunction keys, as will also be appreciated by those skilled in the art.

The microprocessor 180 may operate at clock speed of tens or evenhundreds of megahertz (or higher) in a typical cellular deviceperforming PDA operations, for example. Yet, such relatively high clockspeeds can introduce digital harmonics in the lines connecting themicroprocessor 180 with the keypad 140. This may result in RFinterference energy, which reduces the sensitivity of the receiver 150.That is, the sensitivity of the RF receiver 150 may be significantlydegraded by the digital noise generated by the microprocessor 180 on theKey-Out and Key-In lines, which is radiated from the keyboard traces andpicked up by the antenna 154.

In accordance with an embodiment of the present invention shown in FIGS.10A and 10B, and another embodiment shown in FIGS. 11A and 11B,electromagnetic interference (EMI) filters 602, 652 are advantageouslycoupled to the Key_In and Key_Out lines to reduce the RF interferencepicked up by the antenna 154. An exemplary EMI filter array 602 isillustrated in FIG. 10B. The EMI filter array 602 illustrativelyincludes series elements formed as resistors R1001 through R1006respectively coupled to Key_Out lines KEY_OUT_0 through KEY_OUT_5, andresistors R1007 through R1011 respectively coupled to key in linesKEY_IN_0 through KEY_IN_4. The values of the resistors R1001-R1011 areselected based upon the parasitic capacitance and/or inductance of theKey_Out and Key_In lines to provide an RC, RL, or RLC filter withdesired filtering characteristics. Yet, these values should also beselected so as not to cause undue signal degradation over the Key_Outand Key_In lines. By way of example, 1K Ohm resistors were used in theillustrated example, although other values may be used in otherembodiments. These series elements formed as resistors and connectedbetween the microprocessor or other CPU circuit and keyboard connectorhas been found advantageous when high Q values are involved. Theresistors could be surface mount resistors on the circuit board 67. Theresistors can be connected in-line with the printed conductive tracesused for Key_Out and Key_In lines. Other configurations are possible, ofcourse.

Moreover, other types of EMI filtering components may be used inaddition to, or instead of, those noted above. For example, resistors,inductors, shunt capacitors, EMI ferrite beads, or a combination thereofmay be used in different embodiments, as will be appreciated by thoseskilled in the art.

An exemplary embodiment of a portion of a circuit for a wireless localarea network (WLAN) device with a similar EMI filter array isillustrated in FIGS. 11A and 11B. The filter array 652 connects to thekey array circuit 650 via the Key_Out and Key_In lines (FIG. 11A). TheEMI filter array 652 illustratively includes series elements formed asresistors R1001-R1006 and R1020 respectively connected to Key_Out linesKEY_OUT_0 through KEY_OUT_6, and resistors R1007-R1011 respectivelyconnected to Key_In lines KEY_IN_0 through KEY_IN_4. Here again, otherseries elements or other filtering arrangements may be used as well.

As noted before with reference to FIG. 3, the keypad 140 may be anumeric keypad array for use in placing cellular telephone calls, aswill be appreciated by those skilled in the art. In the embodimentillustrated in FIG. 3, the device 20 advantageously provides personaldigital assistant (PDA) and/or email/Internet functionality. As such,the keypad 140 illustratively includes alphanumeric keys and otherfunction keys, to allow text typing as well as number entry for placingphone calls.

During transmission, radio frequency (RF) energy from the transmitter152 and its associated antenna 156 can interfere with or couple to theinput/output (I/O) lines of the microprocessor 180 through the KEY_INand KEY_OUT lines connecting the microprocessor and the keypad 140. Thisinterference may cause a variety of problems, potentially as severe asresetting the microprocessor. This is especially problematic with thehigher power GSM cellular phones and assorted communications devicesthat operate with about two (2) watts and higher output power. This, inturn, could cause a user to lose a message or other document inprogress, or to be cut off during a phone call, for example.

In accordance with one embodiment of the present invention shown in FIG.12, a keypad connector 700 is positioned on a separate keyboard and isoperatively connected to a keypad array circuit 720 shown in schematiccircuit diagram. This keypad connector operates as a keyboard connectorthat connects to the keyboard connector on the circuit board. Variouslight emitting diodes (LED's) 730 are connected to the keypad connector.Test points 732 are illustrated as operatively connected to the keypadarray circuit. The keypad connector 700 can be similar in design as thekeyboard connector 600 except with a reverse configuration to allow theconnectors to clip or connect together. In the embodiment shown in FIG.12, a plurality of series connected elements, e.g., resistors R1-R8, areadvantageously coupled to the KEY_IN and KEY_OUT lines on the separatekeyboard to dampen RF energy picked up by these lines, either from theantenna 156 or from external interference. The values of the resistorsR1-R8 are carefully chosen based upon the parasitic capacitance and/orinductance of the Key-Out and Key-In lines to provide an RC, RL, or RLCfilter with desired filtering characteristics. However, it is importantthat these values not be so large that they effect the normal operationof the microprocessor 180 and/or the keyboard 140.

In the example illustrated in FIG. 12, the resistors R1-R8 are all 500Ohm resistors, although other resistor values may be used in differentembodiments. The series elements, e.g., resistors R1-R8, are preferablypositioned on the keyboard itself adjacent the keys. For example, theresistors R1-R8 may be surface mount resistors on a keyboard printedcircuit board (PCB) or other board, such as a main board 67, and theresistors may be connected in line with the printed conductive tracesused for the Key_Out and Key_In lines. Of course, other configurationsknown to those skilled in the art are also possible.

In addition, other types of EMI filtering components may be used inaddition to, or instead of, those noted above. For example, resistors,inductors, shunt capacitors, EMI ferrite beads, or a combination thereofmay be used in different embodiments, as will be appreciated by thoseskilled in the art. It should also be noted that the above-described EMIfiltering components may be used in devices other than cellular devices,such as mobile handheld wireless local area network (WLAN) devices, forexample, as will be appreciated by those skilled in the art. Operativewith the keyboard connection are Light Emitting Diodes (LED's), whichemit light therefrom.

This application is related to copending patent applications entitled,“MOBILE WIRELESS COMMUNICATIONS DEVICE WITH REDUCED INTERFERING ENERGYFROM THE DISPLAY AND RELATED METHODS,” “MOBILE WIRELESS COMMUNICATIONSDEVICE WITH REDUCED INTERFERING ENERGY INTO AUDIO CIRCUIT AND RELATEDMETHODS,” “MOBILE WIRELESS COMMUNICATIONS DEVICE WITH REDUCEDINTERFERENCE FROM THE KEYBOARD INTO THE RADIO RECEIVER,” and “MOBILEWIRELESS COMMUNICATIONS DEVICE WITH REDUCED INTERFERING ENERGY FROM THEKEYBOARD,” which are filed on the same date and by the same assignee andinventors.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

That which is claimed is:
 1. An electronic device comprising: radiofrequency (RF) circuitry; a microphone susceptible to RF interferencefrom the RF circuitry; an RF shield surrounding the microphone; a coveradjacent the RF shield; an acoustical tube extending between the RFshield and cover; and an electrically conductive ring surrounding theacoustical tube and extending between opposing surfaces of the RF shieldand cover.
 2. The electronic device according to claim 1, furthercomprising a circuit board mounting the RF circuitry, microphone and RFshield.
 3. The electronic device according to claim 1, furthercomprising a power amplifier coupled to the RF circuitry.
 4. Theelectronic device according to claim 1, further comprising an antennacoupled to the RF circuitry.
 5. The electronic device according to claim4, wherein the antenna comprises a dielectric substrate and at least oneconductive trace thereon.
 6. The electronic device according to claim 1,wherein the RF shield and the cover each comprises metal.
 7. Theelectronic device according to claim 1, wherein the RF circuitrycomprises a transceiver chip set.
 8. The electronic device according toclaim 1, wherein the RF circuitry is operative for generating GlobalSystems for Mobile (GSM) packet bursts.
 9. The electronic deviceaccording to claim 1, further comprising an isolation compartmentcontaining the RF circuitry.
 10. The electronic device according toclaim 1, wherein the microphone comprises a surface mounted microphoneand associated filter component.
 11. The electronic device according toclaim 1, wherein the cover has a sound opening therein having a diameterof about 2.0 mm or less.
 12. An electronic device comprising: radiofrequency (RF) circuitry; a surface mount microphone susceptible to REinterference from the RE circuitry; a metallic RE shield surrounding themicrophone; a metallic cover adjacent the metallic RF shield; anacoustical tube extending between the metallic RE shield and metalliccover; and a metallic ring surrounding the acoustical tube and extendingbetween opposing surfaces of the metallic RF shield and metallic cover.13. The electronic device according to claim 12, further comprising acircuit board mounting the RF circuitry, microphone and metallic REshield.
 14. The electronic device according to claim 12, furthercomprising a power amplifier coupled to the RE circuitry, and an antennacoupled to the RE circuitry.
 15. The electronic device according toclaim 12, wherein the RF circuitry comprises a transceiver chip set. 16.The electronic device according to claim 12, wherein the RF circuitry isoperative for generating Global Systems for Mobile (GSM) packet bursts.17. A method for making an electronic device comprising radio frequency(RE) circuitry, a microphone susceptible to RE interference from the REcircuitry, and a cover adjacent the microphone, the method comprising:positioning an RF shield surrounding the microphone; extending anacoustical tube between the RE shield and cover; and positioning anelectrically conductive ring surrounding the acoustical tube andextending between opposing surfaces of the RE shield and cover.
 18. Themethod according to claim 17, further comprising mounting the RFcircuitry, microphone and RF shield on a circuit board.
 19. The methodaccording to claim 17, wherein the RF shield and the cover eachcomprises metal.
 20. The method according to claim 17, wherein the REcircuitry comprises a transceiver chip set.
 21. The method according toclaim 17, wherein the microphone comprises a surface mounted microphoneand associated filter component.